Ferroalloy casting process



Filed Feb. 1, 1966 Mill Balls Lifr Back of Chill Suspenswn Bars Walla:

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Exposed Surface Dross Area M Y n M .w W m m S n H M. W K Y 1 5 R B 8 l 7United States Patent 3,373,794 FERROALLOY CASTING PROCESS Richard A.Crago, Grand Island, N.Y., assignor to Union Carbide Corporation, acorporation of New York Filed Feb. 1, 196 6, Ser. No. 524,139

2 Claims. (Cl. 164-127) The present invention relates to the casting ofalloys. More particularly the present invention relates to the castingof magnesium ferrosilicon.

In the past, ithas been the usual practice in making magnesiumferrosilicon for use as an addition agent to pour the molten alloy intolarge open chills up to about five to six inches deep and about fivefeet by five feet in section. The cast metal was permitted to air-cooland the solid product was then subjected to crushing to obtain asuitable industrially sized product of say 1% inches by inch.

There are several drawbacks to this prior process for example since alarge portion of the molten metal was exposed to air while cooling inthe chill a substantial layer of objectionable magnesium oxide wasformed which had to be removed before sale and use of the product andthis led to a significant loss of magnesium. Further, the segregation ofmagnesium is severe and in the usual product the magnesium for a nominal9% Mg alloy would range from 12-15% at the top of the casting to 4-7% atthe lower part of the casting. This situation is economicallydisadvantageous since, after the alloy is crushed to size, to be on thesafe side, the user frequently assumes that the magnesium content of theparticulated alloy is less than the nominal value.

It is therefore an object of the present invention to provide a processfor casting magnesium ferrosilicon whereby the loss of magnesium due tooxidation can be avoided.

It is a further object of the present invention to provide a process forcasting magnesium ferrosilicon whereby improved uniformity of magnesiumdistribution is obtained.

Other objects will be apparent from the following description and claimstaken in conjunction with the drawing in which:

FIGURE 1 shows, in elevation and somewhat schematically, apparatus forthe practice of this invention,

FIGURE 2 shows a modification of the apparatus of FIGURE 1, and

FIGURE 3 shows the plan view of the apparatus of FIGURE 2.

A process in accordance with the present invention comprises preparingmolten magnesium ferrosilicon; pouring the molten magnesium ferrosiliconinto a chill; providing a metal member in contact with the upper surfaceof the molten magnesium ferrosilicon; causing the molten magnesiumferrosilicon to solidify in the chill in contact with said metal member;removing the metal member after solidification of the magnesiumferrosilicon and removing the solidified magnesium ferrosilicon from thechill.

The following Table I shows the composition of magnesium ferrosiliconalloys which can be advantageously cast in accordance with the presentinvention:

The present invention will be more clearly understood by reference tothe drawing which in FIGURE 1 shows at 1 a conventional chill forcasting magnesium ferrosilicon. The chill for example can be made ofcast iron 3,373,794 Patented Mar. 19, 1968 with a base about 4-6 inchesthick and side walls about 5-10 inches in height tapering in width from6 inches to 4 inches. In practicing the invention molten magnesiumferrosilicon is prepared by any suitable technique. For example,magnesium can be plunged into molten ferrosilicon alloy to give adesired magnesium content e.g. about 9%. With the molten magnesiumferrosilicon in the temperature range of about 1225 to 1300 C., themetal 3 is poured into the chill 1 which is provided with a removablemetal cover 5, which can be a steel billet about 4-6 inches thick ormore and which is conveniently supported on steel mill balls 7. Arelatively small opening between the chill and the billet is provided at9 for the entry of the molten metal which as shown is in an amountsufiicient to contact the metal member 5 and be substantially coveredthereby. As illustrated in the drawing, by inclining metal cover member5 slightly to the horizontal, the dross, i.e. low density impuritieswhich are usually present, separate at the small exposed surface of themolten metal and surface contamination of the magnesium ferrosilicon isavoided.

The molten metal cast into the chill as aforedescribed freezes andsolidifies, the solidification progressing concurrently from both thetop and bottom of the chill, with the result that the magnesiumsegregation characteristic of castings prepared by prior methods isavoided. That is to say that the condition of high magnesium materiali.e. 12-15% at the top of the casting, 4-7% at the bottom, is avoided bycausing concurrent freezing of the casting at the top and bottom thuspreventing separation of the lower melting and lower density magnesiumsili con phase. As a result of this casting process, not only ismagnesium loss eliminated since the covering metal member preventscontact with the air, but magnesium distribution is highly uniform fromtop to bottom in the casting.

Furthermore, upon lifting metal member 5 by way of ring 11, the castingcan be easily removed from the chill and readily crushed to industriallysuitable size, in the course of which the supporting steel balls arerecovered, and since there is practically no oxide formation on thecasting, cleaning of the material is unnecessary.

With reference to FIGURES 2 and 3 which show different views of amodification of the apparatus of FIG- URE 1, it can be seen that the useof steel balls for supporting the removable chill cover 5 can beeliminated by using suspension bars 13 in the manner indicated. FIG-URES 2 and 3 also show that the small exposed area of the casting can befurther decreased by providing a pouring hole 15 in the removable coverand dimensioning the cover so that it closely fits the chill.

The following examples will further illustrate the present invention.

Example I Molten magnesium ferrosilicon containing 9% magnesium wasprepared and at a temperature of about 1250 C. was cast into a chill.The chill was similar to that shown in the drawing having a basethickness of 6 inches. A steel billet 5 x 5' x 6" was suspended over thechill also as shown in the drawing and was arranged with its lowersurface about 5 inches from the bottom of the chill. The moltenmagnesium ferrosilicon poured into the chill was in contact with thesteel billet at its upper surface and was substantially covered. Aftersolidification of the metal in the chill, the casting, 5 inches thick,was removed and examined. There was no oxide on the surface of thecasting and analysis showed the following magnesium analysis:

Percent mg. Top of casting 10.99 Bottom of casting 8.47

Example ll ysis of the casting after removing the oxide layer showed thefollowing:

Percent mg. Top of casting 12.06 Bottom of casting 4.94

From the foregoing description and examples it can be seen that thepresent invention provides a simple and effective way to obtain higherrecoveries of magnesium in magnesium ferrosilicon castings and alsoprovides castings having an improved magnesium distribution, thusconstituting a significant industrial advance in the art.

What is claimed is:

1. A process for casting magnesium ferrosilicon which comprisespreparing molten magnesium ferrosilicon, pouring the molten magnesiumferrosilicon into a chill, providing a metal member in contact with theupper surface of the molten magnesium ferrosilicon in the chill, saidmetal member substantially covering the upper surface of the moltenmagnesium ferrosilicon, causing the molten magnesium fer-rosilicon tosolidify in the chill in contact with said metal member, removing themetal member after solidification of the magnesium ferrosilicon andremoving the solidified magnesium ferrosilicon from the chill.

2. A process in accordance with claim 1 wherein molten ferrosilicon iscast into a chill having a removable cover and wherein the molten metalis poured into the chill in an amount sufficient to make contact withthe cover.

References Cited UNITED STATES PATENTS 1,484,076 2/ 1924 Perry 249--174XR 1,491,881 4/1924 Perry 249-174 XR 1,494,021 5/1924 Robbins 164-471,716,833 6/1929 Rich 164125 XR FOREIGN PATENTS 516,533 1/ 1940 GreatBritain. 833,609 7/1938 France.

43,818 3/ 1927 Norway.

J. SPENCER OVERHOLSER, Primary Examiner. VERNON KILBOURN RISING,Assistant Examiner.

1. A PROCESS FOR CASTING MAGNESIUM FERROSILICON WHICH COMPRISES PREPARING MOLTEN MAGNESIUM FERROSILICON, POURING THE MOLTEN MAGNESIUM FERROSILICON INTO A CHILL, PRO VIDING A METAL MEMBER IN CONTACT WITH THE UPPER SURFACE OF THE MOLTEN MAGNESIUM FERROSILICON IN THE CHILL, SAID METAL MEMBER SUBSTANTIALLY COVERING THE UPPER SURFACE OF THE MOLTEN MAGNESIUM FERROSILICON, CAUSING THE MOLTEN MAGNESIUM FERROSILICON TO SOLIDIFY IN THE CHILL IN CONTACT WITH SAID METAL MEMBER, REMOVING THE METAL MEMBER AFTER SOLIDIFICATION OF THE MAGNESIUM FERROSILICON AND REMOVING THE SOLIDIFIED MAGNESIUM FERROSILICON FROM THE CHILL. 